1. The Field of the Invention
This invention relates to digital computers. More specifically, the present invention relates to devices used to expand the ability of an existing computer to utilize additional hardware and provide additional features for the user of the computer.
2. The Prior Art
The widespread use of computers in industrial societies has brought the benefits of computers to large numbers of people. In particular, the standardization and availability of personal computers has provided that each user can customize such computers with a wide variety of hardware and software. Unfortunately, some users who want to add hardware to their computer find that all available expansion slots or ports which can accommodate such hardware have already been utilized in their computer. Thus, the user must forego adding one or more hardware items.
The problem of adding hardware is particularly troublesome to users of portable computers. Such portable computers commonly are generally classified into laptop, note book, sub-note book, and palm top size classes. The small size of these computers requires that all of the components associated therewith be miniaturized. In order to allow the user to add hardware to such portable computers, an industry standard promulgated by the Personal Computer Memory Card International Association (PCMCIA) has gained wide acceptance. Such hardware is commonly referred to as a PC Card or a CardBus Card and is known as "PC Card compliant," "PCMCIA compliant" or "CardBus compliant." PC cards and CardBus Cards are compacq hardware devices having dimensions of about 2.1 inches by about 3.4 inches with a thickness of only 3.5 mm, 5 mm, 8 mm or some other dimensions allowed by the promulgated standard. The PC Card typically slides into a socket provided on the side of the portable computer to allow easy replacement of one PC Card with another PC Card. Increasingly, users of desktop computers, as well as other electronic devices, are also using such cards to add hardware devices to their computers.
Widely used hardware devices such as modems, random access memory, and disk drives, for example, are all available as PC cards and will soon be available as CardBus Cards. There are, however, numerous hardware devices which are not yet available, or which may never be available, in a PC Card implementation or a CardBus Card implementation. Thus, portable computer users are unable to use the myriad of hardware devices which are available to desktop computer users. Also, many portable computers do not provide additional ports for communication with hardware devices such as keyboards and pointing devices. For the foregoing reasons, portable computer users are unable to utilize many hardware devices which are utilized by other computer users.
In order to provide computer users with additional expansion capability and convenience of use for their computers, devices referred to as "port replicators" and "expansion chassis" have been provided. These devices provide additional locations for other hardware devices to interface with a computer. These other hardware devices may be stand alone, or external, devices which are commonly configured to communicate with the computer via a serial port using the widely known RS-232 communication protocol. Alternatively, these other hardware devices may be internal devices which are merely printed circuit cards adapted to be installed inside the computer case and which comply with the Industry Standard Architecture (ISA) standard or the Peripheral Component Interconnect (PCI) standard. Port replicators and expansion chassis can also be used to provide added convenience for a portable computer user by making connections to an external key board, external video monitor, and the like, simpler than if each external device needed to be connected to and disconnected from the portable computer.
The previously available port replicators and expansion chassis provide a few useful functions. Disadvantageously, such devices cannot interface with a PCMCIA socket provided in portable computers. Moreover, in many previously available port replicator devices and expansion chassis, only particular types of expansion devices and/or expansion devices which comply with only a less popular standard can be used. Alternatively, some previously available port replicators and expansion chassis utilize non-standard or proprietary connectors and protocols which seriously limits their usefulness.
In view of the foregoing, it would be a significant advance in the art to provide an improved system and method for expanding a computer which overcomes the drawbacks and disadvantages found in the previously available devices.